[ARM] Cleanup ARM includes

arch/arm/kernel/entry-armv.S has contained a comment suggesting
that asm/hardware.h and asm/arch/irqs.h should be moved into the
asm/arch/entry-macro.S include.  So move the includes to these
two files as required.

Add missing includes (asm/hardware.h, asm/io.h) to asm/arch/system.h
includes which use those facilities, and remove asm/io.h from
kernel/process.c.

Remove other unnecessary includes from arch/arm/kernel, arch/arm/mm
and arch/arm/mach-footbridge.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-footbridge/dma.c b/arch/arm/mach-footbridge/dma.c
index a6b1396..7a54578 100644
--- a/arch/arm/mach-footbridge/dma.c
+++ b/arch/arm/mach-footbridge/dma.c
@@ -15,6 +15,7 @@
 
 #include <asm/dma.h>
 #include <asm/io.h>
+#include <asm/scatterlist.h>
 
 #include <asm/mach/dma.h>
 #include <asm/hardware/dec21285.h>